Detached lever timing movement for mechanical time fuze

ABSTRACT

This invention relates to a timing mechanism for a mechanical fuze. The timing movement utilizes the detached lever escapement principle and is designed with elements having a minimum of masses, pivot diameters and eccentricities from the spin axis, so that sensitivity to the effects of spin and setback in excess of 30,000 rpm and 30,000 g&#39;&#39;s, is reduced.

United States Patent 1 Popovitch et a1.

1 1 DETACHED LEVER TIMING MOVEMENT FOR MECHANICAL TIME FUZE [75] Inventors: Dragolyoub Popovitch, Denville,

N.J.; Roy B. Nystrom, East Northport, N.Y.; Melvin Eneman, New York, N.Y.; Carl Biro, Yonkers, N.Y.; Selwyn Alpert, Brooklyn, NY.

[73] Assignee: The United States of America as represented by the Secretary of the Army, Washington, DC.

[22] Filed: Nov. 6, 1968 [21] Appl. No.: 774,231

[52] 11.5. C1. 102/84, 102/71 [51 1 Int. Cl. F42c 9/04 [58] Field of Search 102/83, 84, 71

[ Mar. 18, 1975 [56] References Cited UNITED STATES PATENTS 4/1946 Middlemiss 102/83 11/1959 Gibbs et a1 4 102/71 Primary ExaminerRobert F. Stahl Attorney, Agent, or FirmEdward .1. Kelly; Herbert Berl; Edward F. Costigan [57] ABSTRACT This invention relates to a timing mechanism for a mechanical fuze. The timing movement utilizes the detached lever escapement principle and is designed with elements having a minimum of masses, pivot diameters and eccentricities from the spin axis, so that sensitivity to the effects of spin and setback in excess of 30,000 rpm and 30,000 gs, is reduced.

8 Claims, 12 Drawing Figures PMENTEB MR 1 8 I975 SHLU l U? 8 FIG.I.

6 Mdand ROY B. NYSTROM MELVIN ENEMAN ATTORNEYS:

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PATENTED 1 81975 3.871 .2498

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PATEIHED HAR I 81975 SHEET 7 OF 8 INVENTORSI CARL BIRO -wm ALPERT H C W V N M WO O M P E BSN UVIE ON U N Bl. w. AY E n URM A'FTORNEYS:

DETACHED LEVER TIMING MOVEMENT FOR MECHANICAL TIME FUZE The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to us of any royalty thereon.

This invention describes a new timing mechanism and is directed to providing a detached lever escapement movement to insure a very high degree of accuracy.

Conventional mechanical time fuzes all use one or another well-refined version of the cylindrical escapement, usually known as the Junghans Escapement. The sophisticated weapons in use today require a device than can withstand extreme environments and provide greater accuracy than is possible with the cylindrical escapement. The timing movement of the invention represents a major advance in the art of mechanical time fuzes in that the much greater inherent accuracy of the detached lever escapement can now replace the five to ten times relatively poorer accuracy of the cylinder escapement which is now almost universally used in one or another of its many forms. In addition, this inherently more accurate type of escapement has been applied in a form which is suitable for use under broader ranges of gun conditions and environments than any time fuze known to the inventors. Many attempts to accomplish this have been made in the past, but none have been successfully reduced to practice. The flaws appear to have included overly massive gear trains and pivots, inadequate escapement design, escessively massive balance wheels, improperly matched torque-frequency-mass relationships, etc. The essence of the invention consists of designing and devising elements with minimum masses, pivot diameters, and eccentricities from the spin axis so that sensitivity to the effects of spin and setback up to 30,000 revolutions per minute and 30,000 gs acceleration respectively is greatly reduced. In order to obtain the high degree of accuracy, a high ratio was established between the energy contained in the balance wheel hairspring system versus the energy lost per oscillation. This was accomplished by incorporating a high frequency of oscillation (80.74 b.p.s.) together with a high amplitude of oscillation (from i90 to il80) and minimum contact of the oscillating balance wheel with its cooperating lever (approximately 20 The environments in which the fuze described in copending application Ser. No. 682,441 is designed to function include rotational velocities from 1,800 to 30,000 rpm with eccentricities of the spin axis with respect to the timing movement axis of up to 0.030 -0.060 inches, after experiencing setback accelerations from 900 to 30,000 gs.

FIG. 1 illustrates the fuze described in great detail in said copending application and is provided with the housing 10. The fuze housing includes the digital setting module 12, which acts to simultaneously set and indicate the safe, point-detonating or timing settings of the fuze. The digital setting module 12 relates the fuze setting with the timing mechanism 14 and the latter provides the delay of fuze firing for a desired period of time and relates fuze settings, made into the digital setting module, to the arming and firing trigger delay module 16. This module performs the two functions of arming delay rotor release and firing pin release. In a properly sequenced firing environment, the bore-safe arming delay module 18 is actuated by the arming and firing trigger delay module 16 and the firing pin 20 is released to initiate the explosive train element 22 retained in the arming delay module 18.

It is the timing movement of the fuze that is the primary key to the fuzes accuracy. The fuze 10 of the invention can be set to a fraction 0.1 second throughout its timing range and has shown an overall zero setting error in the order of 0.03 second based on 5 second firings. The mean time of fuze functioning has characteristically been within 0.1 second of set time at 5 second settings and within 0.25 second of set time at 1 15 seconds. This should greatly facilitate its use without extensive range tables. The standard deviation of fuze functioning time is relatively invariant from nonspinning laboratory conditions to 15,000 rpm and 30,000 rpm in the shell. This standard deviation has been from about 0.02 0.05 second at 5 seconds setting to about 0.12 0.25 second at seconds. This greatly improved fuze accuracy permits the most economic exploitation of currently available ballistic accuracy.

It is the primary object of the invention to provide a timing movement for a fuze that is of extremely fine accuracy.

It is another object to provide a timing movement for a spinning fuze that contains its most sensitive elements hairspring, balance wheel, escape wheel on the nominal central axis of rotation to minimize the effects of high rotational speed on accuracy.

It is another object to provide a detached lever timing movement for a spinning fuze that contains a lever con.- figuration having a minimum of mass and a pivot location which is as close as possible to the axis of fuze rotation.

It is yet another object to provide a timing movement structure which can tolerate the high spins and setback that may occur.

It is still yet another object to provide a unique form of hairspring whereby the balance wheel configuration and hairspring combine to achieve a high frequency and high amplitude with a minimum of hairspring length.

And it is still yet another object to provide a timing movement that has general application and is capable of use universally to control or release mechanical or electrical mechanisms.

It is a feature of the invention to utilize a single detent on the balance wheel to restrain operation. Two or more detents may be used if otherwise required.

These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, an embodiment in accordance with the present invention, and wherein:

FIG. 1 is a vertical, sectional view of a fuze incorporating the timing mechanism of the invention,

FIG. 2 is vertical section of the timing mechanism,

FIG. 3 is a plan view of the detached lever escapement elements,

FIG. 4 is a plan view of the first plate assembly and is taken on the line 44 of FIG. 2,

FIG. 5 is a plan view of the balance wheel assembly and is taken on the line 5-5 of FIG. 2,

FIG. 6 is a plan view of the lever assembly and is taken on the line 6-6 of FIG. 2,

FIG. 7 is a plan view of the escapement wheel assembly and is taken on the line 7-7 of FIG. 2, FIG. 8 is a plan view of the barrel spring housing and is taken on the line 8-8 of FIG. 2,

FIG. 9 is an exploded view of the timing movement of the invention,

FIG. 10 is an illustration of the escape lever of the invention,

FIG. 11 illustrates the balance staff assembly, and

FIG. 12 is a detail of the balance wheel construction.

Referring to the FIGS., and particularly to FIG. 9, the timing mechanism of the invention is illustrated in exploded view for greater clarity. The timing movement consists of a hairspring assembly 24, a hairspring regulator 26, a balance wheel assembly 28, a lever assembly 30, an escape wheel assembly 32, a No. 1 gear assembly 34, a No. 2 gear assembly 36, a setback detent assem bly 38 and spin detent assembly 40. The said components are housed in a cavity formed within the plates 42, 44, 46, 48, 50 and 52 with the hairspring assembly 24, the hairspring regulator 26 protruding from plate 42.

Referring to FIG. 2, the input and the output for the timing movement is in the mainspring assembly. The mainspring assembly consists of the housing 56 which has an arbor shaft 58. The arbor shaft is hollow and is slotted (not shown) to retain one end of the mainspring 60. The mainspring 60 provides the input torque and is wound in its assembly by externally engaging the ring gear 71 and is held coiled by the screw 62. A lower ring gear 64 is seated in the hollow shaft 58 and engages the pinion 66 of the No. 2 gear assembly 36. The timing scroll disc 68 is the output and is secured to the lower end of the hollow shaft 58. The timing scroll disc 68 has a spiral groove on its lower face (not shown) to provide a delay in actuating a mating mechanism. The details of the scroll disc and its operation is described and claimed in the above identified co-pending papent application. An outer housing 70 extends over the mainspring housing 56 and is positioned over the annular ring gear 71 of the mainspring housing 56.

The plate member 52 supports the pinion 66 which engages the ring gear 64 and is aligned with the plate member 50 by means of the aligning pins 72 which extend through the apertures 74 and 76 respectively. The fastening screws 78 extend through the holes 80 and 82 to secure the plate members 50 and 52 together. Pinion 66 and gear 84 comprise the No. 2 gear assembly 36. The pinion 66 fits into an opening (not shown) in the plate 52 while the gear 84 is received in the larger portion of the pear-shaped opening 86 of the plate 50 and serves to enmesh the pinion 88. The pinion 88 and the gear 90 comprise the No. 1 gear assembly 34. The gear 88 is retained in the smaller portion of the opening 86. The gear assembly members 34 and 36 are seated in the apertures 94 and 92 of the plate 48 respectively. The aligning pins 96 extend through the apertures 98 found in the plates 42, 44, 46, 48 and 50. The fastening screws 100 extend through aligned apertures 102 to retain the device as a unit.

The timing movement comprising the detached lever escapement structure is best shown in FIGS. 3, 4, 5, 6 and 9. These consist of the folded lever assembly 30 (see FIG. 10), the escape wheel assembly 32, and the balance wheel assembly 28. The escape wheel assembly 32 includes a pinion gear 104 and a gear member 106 which is seated in the aperture 108 of the extension lip 110 left by the elongated groove 112 on the plate 48. The groove 110 actually is cut through the plate 48 to provide the opening 114 into which the folded lever assembly 30 extends. As is evident in FIGS. 3 and 11, the lever assembly 30 consists of a flat lever portion 116 having a pair of divergent arms 118 and dependent pallet pins 120 adapted to extend between the teeth 122 of the escape wheel 106. Obviously, the invention is not limited to the pin construction, since it is also feasible to bend the extremities of the divergent arms 118 to obtain the same function as the pallet pins 120. A forked protrusion 124 extends from between the lever arms 118 of the lever portion 116 at an acute angle to end in two divergent tine members 126 and a central tine 128. The extremeties of the tines 126 are configured as forked ends 130 while the central tine 128 terminates in an arrow tip 132, for a purpose soon to be described. A lever staff assembly 134 enables the folded lever assembly to seat in an aperture 108 whereby the pallet pins 120 extend through the elongated groove or opening 112 to ride between the gear teeth 122.

The balance wheel assembly 28 includes a balance wheel 136 and a balance wheel staff 138. The balance wheel 136 (see FIGS. 3, 4 and 5) has light and dark striations 140 on the rim for frequency calibration of the timing movement. This is performed with the aid of specially designed electro-optical equipment. The striations 140 may be replaced by equivalent light interrupting elements of eliminated if the electro-optical equipment is not needed. A pair of diametrically opposed detent slots 142 are provided in the balance wheel 136 and engage the detent pin 144 of the spin detent assembly 40. This function will be described shortly in greater detail. The balance wheel staff contains an impulse pin 146 which oscillates in an are as the balance wheel oscillates. This pin 146 can impact the inner edge of either lever fork element 130 of the lever 30. The kinetic energy of the escape wheel is transferred to the lever by the impulse of the escape wheel teeth 122 with the pallet pins 120 on the lever arms 118. The ki netic energy of the lever is transferred to the balance wheel assembly 28 by the impulse pin 146 as it rides in the lever fork 130. The folded lever 30 has safety pin 132 which rides in the crescent 148 (see FIG. 11), on the balance wheel staff 138 to assure that the impulse pin 146 and the fork 124 of the lever 116 engages at the proper interval during a clock cycle. These locking, unlocking, impulse and safety functions are entirely similar to those of any contemporary detached lever clockwork.

The timing movement is normally prevented from running by the said detent assemblies 38 and 40. The spin detent spring 150 (see FIG. 5) is seated in the slot 152 of the plate 46 and engages the spin detent 156 which in turn is pivotally retained on the pin 158 extending from the plate 48 into the cut-out portion of the plate 46. The setback pin 154 is forced into engagement with the spin detent 156 by means of the compression spring 157. The spring 157 is held in the aperture 159 of the plate 46. The detent pin 144 of the spin detent 156 seats in the balance wheel slot 142. The rotatable, spring-opposed, spin detent 156 directly engages the balance wheel assembly 28, being released by spins in excess of 1000 rpm. The sliding setback pin detent 154 by being spring-opposed, blocks release of the spin detent 156 until setback in excess of 900 gs is experienced. Upon firing, first the setback detent 154 slides rearward because of the setback and the spring 157 is compressed. Then the spin detent 156 turns outward, releasing the balance wheel assembly 28 and is blocked from returning because the setback detent has not resumed its original position as the setback forces have subsided.

The kinetic energy transferred to the balance wheel assembly is stored by a torsion wire hairspring 162 having a circular cross section. Any other cross-section would also be suitable, if the additional length, needed to provide the same angle of rotation, was available. It is housed in the hairspring assembly 24 with one end clamped to the hairspring regulator 26 at 164 and the other end fixed to the balance wheel staff 138 at 166. The effective length of the hairspring is adjustable by means of the hairspring regluator sleeve 168 retained as the hairspring assembly 26 by the locknut regulator 170. The lockpin regulator 172 is secured to the sleeve 168. The tip 174 of the balance wheel assembly 28 is seated in the aperture 108 of the lip 110 opposite the escape wheel assembly 32, as is best illustrated in FIG. 2. The torsion wire hairspring is angularly displaced by the angular displacement of the balance wheel assembly. This stores energy in the torsion wire hairspring, which tends to rotate the balance wheel assembly in the direction opposite to its original displacement. By wellknown principles, the balance wheel-hairspring assembly thus produces oscillations ofa highly consistent frequency over a broad range of oscillatory displacements. Because the maximum spin environment of the fuze creates a severe centrifugal force loading on escapement components proportional to their distance from the fuze spin axis, it was beneficial and necessary to locate the components as close to the spin axis as possible. For this reason, the escapement for the fuze l0 incorporates the folded lever 30 which permits the escapement to be on two (2) axis. These two axis are the coincident balance wheel, hairspring and escapement wheel rotational axis, which are nominally on the fuze spin axis and the folded lever rotational axis.

Fuze setting is obtained by mating a setting tool into the nose portion of the fuze, engaging the setting key 176, (see FIG. 1) and turning in a counterclockwise position from the safe-set position. A range ofO 2OO seconds is obtained. The 200 second characteristic may be easily increased or reduced as needed. When the digital counter I2 is operated, the entire timing mechanism module, which includes the timing disc scroll 68, is turned clockwise. The balance wheel assembly 28 is locked by the spin detent 156 with a relatively large angular displacement from its central position. In this locked position, the hairspring 162 is twisted and thereby is applying a torque attempting to turn the balance wheel toward its central position. Upon experiencing the proper fuze environment, the timing movement functions. The propelling force of the environment causes a setback which forces the setback spring and the setback pin 154 to move and release the spin detent 156 from engagement in the detent slot 142 of the balance wheel 136. The balance wheel assembly 28 is thus freed to be turned by the hairspring assembly 24. In being turned toward its central position, the balance wheel assembly 28 carries its impulse pin 126 into impact with the inside face of one of the two fork ends I30 of lcvcr assembly 30. This impact turns the lever assembly 30 about the lever staff 134. In turning, the

lever assembly 30 first moves one of its pallet pins from a locking position against one of the escape wheel teeth 122 to a position in which the unlocked tooth may drive against the pallet pin 120 which had been locking it. By this means the escape wheel tooth 122 is enabled to drive the pallet pin 120, which thus turns the lever assembly 30. The inside face of the fork end which was impacted by the impulse pin 146 at this point receding from the path of the impulse pin and the inside face of the other fork end 130 is driven against the impulse pin 146 by the continued and driven turning of the lever assembly 30. The driving escape wheel tooth 122 continues past the driven pallet pin 120. Before this occurs, the second pallet pin 120 is introduced in front of a second escape wheel tooth 122 so that when the driving escape wheel tooth drops free of the driven pallet pin, the second pallet pin is in position to lock the second escape wheel tooth. The escape wheel assembly 32 and lever assembly 30 are now in position to repeat the sequence of operations described except that the lever would be oscillated in a direction opposite to its first motion. This second sequence would start when the balance wheel assembly 28 has completed its free oscillation and has been returned toward its central position by the restoring torque of hairspring assembly 24. In short, the timing movement is now operating in the well-known manner of a detached lever escapement. The torque of the mainspring 60 turns the timing scroll member 68 at a rate governed by the escape wheel gear member 106 and the gear ratio between the escape wheel pinion 104 and the lower ring gear 64 on the arbor shaft 58. The timing scroll member 68 turns clockwise the spiral path 178. At the time of setback, a setback pin in the trigger delay module 16 moves clear of the safety lever when then is rotated by spin forces. The follower pin moves in the spiral path 178. When reaching a predetermined surface, the rotor detent lever 182 is released. The rotor detent assembly and the arming delay rotor are then released. Further rotation of the scroll 68, corresponding to at least a minimum time to allow operation of the arming delay rotor, frees the follower pin 80 and permits the firing arm shaft to rotate and actuate the firing pin release lever 184 to release the firing pin 186. This initiates the explosive train to explode the projectile. The operation of the fuze itself is described in greater detail in the copending application.

It is to be emphasized that the timing movement is not necessarily limited to the fuze application discussed. Modifications to balance wheel assembly inertia have produced timing movement operating frequencies over a range of 5 beats per second to 725 beats per second. Additional modifications to hairspring length and cross-section would yield a greater range.

In addition, the output of the timing movement need not be of the form of the timing scroll disc 68. A variety of output disc configurations can be utilized to yield a required timing delay or sequence of time delays.

Substitution of elements of modifications would be within the scope of the conception. Other modifications within the scope of the invention include:

I. Modification of frequency by change in balance wheel inertia over a range exceeding reduction of rate to one tenth or increase by 10/1.

2. Variation in gear ratio or mainspring torque.

3. Substitution of rectangular or other section wire for the round wire hairspring described.

4. Substitution of other means of locking and unlocking the movement to permit its operation.

5. Locking the movement by means of locking elements other than or in addition to the balance wheel.

It is thus obvious that the invention may be practiced in many forms without departing from its scope, and is limited only by the structure of the appended claims.

What is claimed is:

l. A timing mechanism for a fuze of the type wherein a lever member operatively engaging a balance wheel assembly, an escape wheel assembly and reciprocating means operatively engaging said escape wheel assembly and adapted to actuate a time delay element of said fuze, the improvement which comprises:

a folded lever member positioned on one side of a common escapement axis operatively engaging said balance wheel assembly and said escape wheel assembly,

a round hairspring operatively engaging said balance wheel assembly and said escape wheel assembly and coaxial with the longitudinal axis of a rotating projectile, permitting said balance wheel oscillation of 1 90 to 1 180 while withstanding a force of 30,000 gs and 30,000 revolutions per minute, and

pivot means operatively engaging said escape wheel assembly, said balance wheel assembly, said folded lever and said hairspring.

2. The combination of claim 1, wherein said escape wheel assembly includes a gear member,

said gear member having teeth means, and

means on said lever member extending between said teeth means, whereby oscillating movement of the lever actuates the gear member for time delay in the detonation of the fuze.

3. The combination of claim 2, wherein said balance wheel assembly includes an impulse member,

said lever member including forked protrusion means, and

said impulse member rides between the tines of the forked protrusion means.

4. The combination of claim 3, wherein said balance wheel assembly includes a crescent shaped portion, and

said lever member includes safety pin means, said safety pin means riding in the crescent of the balance wheel assembly. 5. The timing mechanism according to claim 1 wherein said balance wheel assembly and said escape wheel assembly have a common axis of rotation and,

said lever member is pivotally supported about an axis in spaced relation to said common axis of rotation for engaging said balance and escape wheel as semblies at points intermediate said common axis and said member axis,

said member being integral and having a pair of radially, oppositely extending portions for maintaining the center of gravity of said member coincident with said member axis whereby a setback force on said lever member will be directed axially thereof.

6. The timing mechanism according to claim 5 wherein one of said pair of portions includes:

a diverging pair of coplanar arms having a common portion proximate said member axis and each carrying at its end a depending pin for operative engagement with said escape wheel assembly,

a third arm intermediate said pair of arms extending from said common portion upwardly and laterally and provided at its free end with means for mechanical engagement with said balance wheel assembly.

7. A timing mechanism for a fuze, comprising:

a balance wheel,

a plurality of detent slots, and

a setback and spin detent means seated in said slots to hold said balance wheel motionless until the fuze is fired wherein a setback pin is seated in said timing mechanism, and

said spin detent means including a detent member pivotally retained in said balance wheel slot,

said setback pin engaging said spin detent means to hold the detent in said slot whereby the balance wheel is inactivated.

8. The combination of claim 7, wherein said balance wheel has dark and light striations for frequency calibration of the timing movement. 5 

1. A timing mechanism for a fuze of the type wherein a lever member operatively engaging a balance wheel assembly, an escape wheel assembly and reciprocating means operatively engaging said escape wheel assembly and adapted to actuate a time delay element of said fuze, the improvement which comprises: a folded lever member positioned on one side of a common escapement axis operatively engaging said balance wheel assembly and said escape wheel assembly, a round hairspring operatively engaging said balance wheel assembly and said escape wheel assembly and coaxial with the longitudinal axis of a rotating projectile, permitting said balance wheel oscillation of + OR - 90* to + OR - 180* while withstanding a force of 30,000 g''s and 30,000 revolutions per minute, and pivot means operatively engaging said escape wheel assembly, said balance wheel assembly, said folded lever and said hairspring.
 2. The combination of claim 1, wherein said escape wheel assembly includes a gear member, said gear member having teeth means, and means on said lever member extending between said teeth means, whereby oscillating movement of the lever actuates the gear member for time delay in the detonation of the fuze.
 3. The combination of claim 2, wherein said balance wheel assembly includes an impulse member, said lever member including forked protrusion means, and said impulse member rides between the tines of the forked protrusion means.
 4. The combination of claim 3, wherein said balance wheel assembly includes a crescent shaped portion, and said lever member includes safety pin means, said safety pin means riding in the crescent of the balance wheel assembly.
 5. The timing mechanism according to claim 1 wherein said balance wheel assembly and said escape wheel assembly have a common axis of rotation and, said lever member is pivotally supported about an axis in spaced relation to said common axis of rotation for engaging said balance and escape wheel assemblies at points intermediate said common axis and said member axis, said member being integral and having a pair of radially, oppositely extending portions for maintaining the center of gravity of said member coincident with said member axis whereby a setback force on said lever member will be directed axially thereof.
 6. The timing mechanism according to claim 5 wherein one of said pair of portions includes: a diverging pair of coplanar arms having a common portion proximate said member axis and each carrying at its end a depending pin for operative engagement with said escape wheel assembly, a third arm intermediate said pair of arms extending from said common portion upwardly and laterally and provided at its free end with means for mechanical engagement with said balance wheel assembly.
 7. A timing mechanism for a fuze, comprising: a balance wheel, a plurality of detent slots, and a setback and spin detent means seated in said slots to hold said balance wheel motionless until the fuze is fired wherein a setback pin is seated in said timing mechanism, and said spin detent means including a detent member pivotally retained in said balance wheel slot, said setback pin engaging said spin detent means to hold the detent in said slot whereby the balance wheel is inactivated.
 8. The combination of claim 7, wherein said balance wheel has dark and light striations for frequency calibration of the timing movement. 